<!DOCTYPE html>
<html lang="en">

<head>
    <meta charset="UTF-8">
    <meta http-equiv="X-UA-Compatible" content="IE=edge">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <title>Document</title>
    <style>
        * {
            margin: 0;
            padding: 0;
            border: 1px solid rgb(48, 47, 47);
        }

        .con {
            display: flex;
            flex-direction: column;
            height: 90vh;
        }

        .con .header {
            flex: 1;
        }

        .con .center {
            flex: 5;
            display: flex;

        }

        .con .center .left {
            flex: 3;
            display: flex;
            flex-direction: column;
        }

        .con .center .left .up {
            flex: 2;
        }

        .con .center .left .down {
            flex: 1;
        }

        .con .center .right {
            flex: 1;
            display: flex;
            flex-direction: column;
        }

        .con .center .right .up {
            flex: 1;
        }

        .con .center .right .center {
            flex: 4;
            display: flex;
            flex-direction: column;
        }

        .con .center .right .down {
            flex: 5;
        }
    </style>
</head>

<body>
    <div class="con">
        <div class="header">
            用户：张胜

        </div>
        <div class="center">
            <div class="left">
                <div class="up">
                    <p>张三：你好</p>
                    <p>李四：你好</p>

                </div>
                <div class="down">
                    <textarea name="" id="" style="width: 80%;height: 100%;"></textarea>
                    <input type="button" value="发送">
                </div>
            </div>
            <div class="right">
                <div class="up">
                    好友列表
                </div>
                <div class="center">
                    <p>张三</p>
                    <p>李四</p>
                </div>
                <div class="down">
                    系统广播
                </div>
            </div>
        </div>
    </div>
</body>

</html>